It has been reported that the gastrointestinal ulcers may be caused by an excessive secretion of acids such as hydrochloric acid or pepsin as well as by an action of anti-inflammatory agents such as indomethacin, toxic chemicals, pathogenic virus or toxic microorganisms. In particular, it had been reported that H.sup.+ /K.sup.+ ATPase, a proton carrying enzyme which occurs in gastric mucosa, is involved in the formation of ulcer caused by a secretion of excess gastric juices.
EP 339768A, EP 0334491A and U.S. Pat. No. 4,343,804 disclose 4-aminoquinoline derivatives having an effective anti-gastric juice secretion activity.
The present inventors surprisingly found out that if quinoline nucleus of 4-aminoquinoline derivatives of the prior arts is replaced with naphthyridine parent-nucleus, the resulting new compounds showed potent anti-ulcer, anti-gastric juice secretion and anti-H.sup.+ /K.sup.+ ATPase activities.